Quality of statistical process control procedures required for manufacturing

Quality assurance in highway
construction projects

Mithilesh Gawali1

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in Construction Engineering and Management (Student), University of Illinois-


Control & Assurance is an integral part in construction projects, mainly
highways, due to the sheer amount of investment made in these projects. The
high number of stakeholders and consumers of this critical piece of
infrastructure, has made it essential to maintain the quality during and after
construction. The necessity of maximizing profits and improvements in
management science has compelled the construction industry to invest in quality
assurance. Additional motivation came from the recent success of management
techniques like Total Quality Management (TQM) in other industries like
manufacturing & services.

paper will discuss the need for a quality assurance program and how it is setup
in the construction industry, primarily in highway projects. The paper studies
the present models and methods for quality control and determines whether there
are any other methods available which can be more cost efficient. New and
innovative methods of ensuring quality control are presented. Lastly, a comparison
between Design-Bid & a Design-Bid-Build type of project system is presented
with respect to their methods and challenges in Quality Assurance.



major factor of USA’s industrial success during the world war was
implementation of statistical process control procedures required for
manufacturing weapons and equipment. Japan adopted these techniques of
statistical control over the manufacturing line where as USA shifted their
focus to profits & productivity. This led to a stagnation in quality
management in the 1960’s & 70’s 2. The Japanese on the other hand were
successful in delivering quality consumer goods at a lower price because of
control over the manufacturing processes. Today, globalization has increased
the competition amongst many industries which is recognized as one of the
compelling factors for pursuing continuous improvement 3. Improved efficiency
achieved due to improved processes has enabled smaller firms in less
competitive environments to achieve higher profit margins. The relative power
of a consumer is enhanced because of the paradigm shift witnessed due to
globalization 4.

States transportation has a value of approximately $7.0 Trillion 1. The major
challenges are to preserve and protect the quality of this huge investment.
Also, the transportation industry is growing with time and the future has its
own sets of challenges like growth in traffic, congestion on both highways
& city roads, and concerns regarding environmental impacts of highway
construction. The shrinking investment into maintaining & enhancing the
critical infrastructure is also a major issue. These factors coupled with
decreasing workforces & a very old highway infrastructure makes quality a
very important factor. These issues will require noteworthy consideration to
guarantee that we get the best possible performance from the highways planned
in future.

History of Quality Assurance in
Transportation Industry

transportation construction, the American Association of State Highway &
Transport Officials (AASHTO) Road Test of 1956 is the first documented event of
incorporation quality assurance techniques in construction of highways 5. A
statistical specification for Hot-Mix Asphalt construction (HMA) was
implemented by Bowers & Lane in 1976 6. Around the same period, many
industries were implementing highway construction specifications while considering
statistical quality control 7. The core of quality assurance systems has
remained the same since the 70’s. But the drive for implementation of a
statistical process control & quality assurance program comes from other
forces which are either inherent to HMA manufacturing or related to the
socio-economic environment in which it operates.

of the most noticeable internal force has been the development of Superpave Mix
design method by the Strategic Highway research program. The essence of a Superpave
Mix-Design is a production control system which allows the designed properties
to be attained. This system takes asphalt, binder, aggregate selection in mix
design along with traffic and climatic control. Thereby, each superpave design
is catered to the specific conditions the roadway is going to be exposed to
which ensures that the designed specifications are met. The Federal Highway
Administration literature states that “By allowing highway agencies to
determine if the mix delivered to the jobsite matches the mix designed in the
laboratory, the QC/QA procedures will ensure that Superpave pavements perform
as expected.” 8 The shortage of raw materials in addition to improvements in
recycling technology have realized the inclusion of recycled asphalt pavement
(RAP) in the HMA industry. The use of RAP has increased the importance of
statistical process control in the HMA industry due to it’s the increased
requirements of attention to manufacturing process because of the difficulty to
control the recycling process. The changed ratios in asphalt binders and
recycled materials have increased the demand of a controlled process to attain
the design requirements. The FHWA & AASHTO also now recognize the value of
Total Quality Management (TQM) and its contributions to quality assurance

External Factors Driving QA programs

most important external factor which drives the implementation of quality
assurance programs is the enhanced competition for taxpayers’ money. A major
part of this money is distributed amongst many other government functions like
education, defense, & healthcare. This makes it essential to make efficient
use of the funds allotted and maximize the value of gained from spending each
dollar. Use of modern management systems is the key to account for the spending
of public funds. Additional motivation for quality-management systems arose
from the successful implementation of TQM in industries like services &
manufacturing. The concepts of TQM are present in other industries as well in
form of lean production (lean construction), just-in-time systems &
six-sigma processes. The National Quality Initiative (NQI) incorporates the TQM
initiatives taken by the construction industry, specially transportation
construction. The last and a major factor is a very fast growth of information
technology tools making the statistical process control easier. This is due to
the abundance of real-time data to all the entities involved in the process of
production. With more developments in the IT sector, the processing speeds and
the connectivity amongst everyone is increasing making it easy to manage the
flow of data required for monitoring the manufacturing processes. In
comparison, the pre-computer era called upon for exhaustive computational
resources for statistical control, whereas, now the required effort is easier
and more cost effective. Some of the most difficult challenges in
implementation of QA programs can now be easily solved by use of Computers,
internet, GPS etc.

Quality Assurance Program

defines quality assurance as “(1) All those planned and systematic actions
necessary to provide confidence that a product or facility will perform
satisfactorily in service; or (2) making sure the quality of a product is what
it should be.” 9 The key documents act as the guidance for implementing
Quality Assurance programs are the 1992 NQI report “National Quality
Improvement Task Force Report on Quality Procedures for Highway Construction”.
10 This document defines the vision for the projects & sets the
foundation necessary to aid the efforts to achieve the vision. The other major
document required is “AASHTO Implementation Manual for Quality Assurance” which
defines a recommended structure for the QA program. 11

the term QC/QA was used wherein QC (Quality Control) referred to the role of a
contractor and QA (Quality Assurance) was the role of an agency. The term meant
that QC & QA were separate terms. 
However, Quality Assurance implies an overall system for promising project
quality with Quality control being one element of a widespread system. A
quality assurance system is comprised of components necessary to make sure that
the quality of a service or a product is acceptable to the customer or the
client. The components are as follows:

1)      Quality Control:
“The sum of the activities performed by either the contractor or manufacturer/producer
to make sure that a product meets contract specific requirements.” 12. The
main purpose of QC is to provide information to the owner/contractor on a time
to time basis to help him in monitoring & guiding production or positioning
processes. Data obtained from QC can also be used for final acceptance
determination by comparing the required quality characteristics to the measured
ones. For the QC data to be accepted for acceptance, it should be subjected to
validation by agency verification test results. External inspectors or
consultants can be employed to conduct Quality Control inspections &
related testing. But this does not replace the agency’s responsibility of
verifying the results. The minimum level of documents to be provided for QC is
specified by the agency and should be fulfilled by the contractor/manufacturer
and related authorities. Typically, QC documentation includes the testing
conditions, results & comparison with benchmarks set forth in the contract

2)      Agency Acceptance:
“The acceptance system defines a set of rational procedures to be used by the
agency to determine the degree of compliance with contract requirements and the
value of the product delivered by the contractor”. 13 This is the responsibility
of the customer. Agency Acceptance includes few basic things:

a.       Supervising
Contractor QC;

b.      Accepting
sampling and testing;

c.       Verification
of QC data

d.      Quality
Measures of acceptance: Limits like Percent-within-limits (PWL) can be used for
data which has a wide acceptance range and a small sample size. If the data is
not suitable for PWL, then the data is compared against engineering limits for

e.       Inspection

3)      Independent Assurance:
“Activities that are unbiased & independent evaluation of all sampling and
testing procedures used in the acceptance program”. 14

motive of an IA system is to ensure the consistency of data used by the agency
to determine acceptance. This is necessary to ensure that any kind of testing
done by the agency and design builder or the contractor follows specific
standards, is done by qualified personnel, and has used proper calibrated
equipment which functions without errors.

4)      Dispute Resolution:
“Formal Procedure used to resolve conflicts resulting from discrepancies
between the Agency’s & Contractor’s results of sufficient magnitude to
impact payment.” 15 This process should be an unbiased one. For addressing
disputes related to testing, the samples used in the testing should be stored
and retained in tamperproof containers and security seals should be placed on
them. The testing should be done by third party laboratories which are

5)      Personnel Qualification:
The requirements of the federal regulation are that qualified personnel must be
involved in both agency acceptance & independent assurance. The contract
documents in case of a design-build type of contract state the minimum
qualifications required for personnel performing QC sampling, inspection &
testing. The quality management personnel should have a thorough comprehension
of QA principles and have an experience of working under those specifications.

6)      Laboratory Accreditation:
All laboratories that are involved in the testing processes in the acceptance
programs must be accredited. The accreditation is to be carried out through the
AASHTO Accreditation Program (AAP). 16 The laboratories that are focused only
on testing for process control are not needed to be certified, but certain
agencies have their own standards which require a certified laboratory for all
tasks. Hence it becomes important for a laboratory to become certified.

7)      Partnering:
“A formal, organized method of improving communication on a project seeking to
minimize disputes, claims & establish a shared commitment to solve problem
in a timely & cost-effective manner” 17. There should be a minimum
partnering objective to avoid situations where the relationships between the
contractor and the owner which can cause impediment in achieving the highest
possible quality.

core elements of a QA program are applicable to any kind of project
irrespective of the delivery method of the project.

Quality Assurance Methods

assurance methods are generally grouped into the following categories: Material
Prequalification, qualification of requirements (for both facilities &
personnel), requirements of submittals, testing of materials, materials
sampling, compliance certificates, inspection & warranties. The methods are
to be used in combination rather than just alone to realize the level of
quality assurance required. The decisions taken after a quality assurance
program/test are based on the use of application of item. The decisions also
are dependent on the consequences of failure of that material on the entire
project. Since construction materials, their manufacturing & testing plays
and important role, material prequalification, methods of Qualification of
Personnel & Qualification of personnel dealing with them are discussed in
detail in this paper.

Material Prequalification

Authorized Materials List

a list of specific materials from various vendors would make sure you always
have a list to refer to for acquiring materials of a required quality. This
involves approaching the vendors and getting samples of mass produced items,
which are to be tested at certified facilities. Before the projects, the
prequalified items are to be tested again and field performance evaluations in
specific project conditions are to be performed to ensure specific quality is
met. Example of eligible materials is concrete components, ready mix concrete,
anchorage systems, safety devices, barrier systems.

Authorized Materials Source List

sources of materials also play an important role in the quality control. This
list can be compiled in the same way as the material list by testing the same
materials available at different sources. Materials from these authorized
material source catalogues should be preferred for use wherever possible.
Examples of such sources are specific location of soil to be used as a
backfill, or use of lime materials in soil stabilization.

Authorized to deliver Material List

is a list of materials which do not require inspections according to specific
projects but only a source inspection is necessary. Source inspection for these
materials must be done at regular intervals irrespective of the projects
schedules. Examples of these materials are sign structures or epoxy coated

Products Manufactured to National
Quality Standards

products are specifically manufactures in a way that they meet the
specifications of organizations like ASTM, AASHTO, AISC. These standards include
criteria which meet national quality standards. These standards can be easily
integrated easily within any agency standards by just incorporating the number,
title or a designation given by the industry. They also provide quality desired
for almost all purposes. These types of materials should be included as much as
possible owing to their capacity to perform according to specifications and are
cost effective alternatives to preparing project specific specifications.

Department Furnished Materials

materials furnished by the contractor which will be incorporated in the project
are included in this list. These can be department owned or department
designed. Examples of these materials include recycled materials, temporary
traffic signs, flashing beacons etc. There are no quality assurance
requirements available in the specifications for department furnished material.

Qualification Requirements for

Prefabrication Audit

agency should perform a prefabrication audit to evaluate a fabricators
processes and his whether he has the resources to deliver the products
according to the quality mentioned in the specifications. This is mainly
applicable to materials which are custom fabricated. Rejection of the material
after field testing is both costly & time consuming and can affect the
quality of the delivered project. The producer’s capability to perform is given
can be assured by the production facility audit. Periodic audit of any
fabricator makes them aware of the responsibility they have to maintain project
quality control.

Authorized Facility Audit Listing

a system based approach to assess the fabricator’s quality control process, the
Authorized facility audit listing (AFAL) is created as list of facilities which
are audited by the agency. This process evaluates the ability of the fabricator
to fabricate products matching the specifications provided in the contractual
documents in terms of the process control maintained at his facility.
Facilities manufacturing iems like structural precast concrete, welded steel
trusses, lighting poles, steel pipe piling are available in the AFAL.

Authorized Laboratory List

agency maintains a list of independent laboratories which are certified to
perform testing on elements like reinforcing steel, splices, guest plates. The
tests performed in such laboratories are production tests for bar
reinforcements, tensile tests for head bar reinforcements & similar tests.
This list helps the agency & contractor by providing them access to
laboratories which can perform tests without disputes amongst them.

Authorized Laboratory

a laboratory to be authorized for testing, it must meet the following prerequisites:

1)      Be
capable of performing tests set forth by the respective agency

2)      Be
currently accredited by AASHTO Accreditation Program (AAP), the relevant agency’s
laboratory accreditation system or a comparable accreditation society which is
recognized by the NCLA (National Co-Operation for laboratory Accreditation.

3)      Must
participate in the lab assessment & proficiency sample services by
recognized organizations dealing with testing of construction materials

4)      Must
be recognized & accepted as an organization which provides product safety
testing & certification.

competence of a laboratory in performing specific test methods is important to
make use of that laboratory for a Quality Assurance program. This can be
demonstrated by having the following personnel & documentation:

1)      Supervisors
with minimum 3years of experience of testing construction materials used in

2)      Routine
laboratory assessments made every 3 years

3)      Training
records demonstrating that the personnel are properly trained & routinely
evaluated, qualified to perform the specific test method.

4)      Authentic
test results showcasing previous experience in successful performance of that
method of testing

5)      A
formal reporting process for results

6)      Records
& a third party certificate showing calibration of the equipment needed for
testing after every 2 years.

Authorized Plant

plant or facility must be certified & authorized to an accepted standard.
Production at any plant can begin only when the authorization process has been
completed. Each agency might have their own criteria for certifying a plant
which needs to be met with.

Qualification Requirement for

ensure that work is performed by competent & qualified contractors only,
the contractors need to be certified by a recognized standard.